Centralized traffic controlling system for railroads



Jun e '1, 1937.

W. T. POWELL CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Filed Feb. 14, 1934 INVENTgb Z00.

ATTORNEY rlllllL Patented June 1, 1937 STATS OFFICE CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR- RAILROADS Application February 14, 1934, Serial No. 711,175

23 Claims.

This invention relates to centralized traflic controlling systems for governing traffic on railroads and more particularly to the interrelation of the communication part of such a system with the traific controlling devices which are supervised thereby.

In a centralized trafiic controlling system of the type contemplated by this invention, communication is established between a central control ofiice and a large number of outlying field stations by means of a station selective coded type of communication system. In a communication system of this type a plurality of series of impulses of difierent code combinations are trans- 5 mitted over the line circuit connecting the control ofiice and the field stations. The first part of each different series of code combinations is employed for the selection of the station. The later part of each different series of code combinations is employed to control the traffic controllingdevices at the selected station.

The present invention pertains more particularly to the manner in which the later part of each different series of code combinations functions to control the controlling devices at the station. More specifically a track switch is governed in accordance with the conditions of switch control relays. Similarly the signals are gov erned by signal control relays which establish the direction, but the particular route over the track switch for such direction is dependent upon a selection which requires that the signal and switch control relays are in correspondence.

These switch and signal control relays receive their selective energizations in accordance with the distinctive character of the impulses comprising the later part of each series of code combinations. The switch and signal control relays are of the neutral type, one for positioning the switch machine to normal, one for positioning the switch machine to reverse, one for clearing signals for east bound traffic (right direction), one for clearing signals for West bound traffic (left direction) and two for putting all signals to stop.

An important feature of the present invention relates to the impulse check arrangement, whereby the recording or the reception of an extra impulse due to a surge or the like on the line at any step of the later part of a series, or the failure to record an impulse at any of these steps cancels or annuls the record for that cycle. This results in the trafiic controlling devices remaining in 55 their former positions instead of being changed to undesired positions due to an improper code being received.

More specifically the code is used to actuate the track switch to normal and to clear the signal for east bound traific. If the first impulse is not recorded or if both a and a is recorded on the first step the switch machine is not operated and the signal is not cleared. If the second impulse is not recorded then the third impulse serves as a check, that is, 10 if it is the east bound signal is cleared but if it is 0 (no impulse) then no signal is cleared. If the first two impulses are properly received and a and a are recorded on the third step, or if no impulse is recorded on the 15 third step no signal is cleared. If thecharacter of the second impulse changes from to or the third changes from to the code plan is such that the signals will all be put to stop rather than a wrong signal being cleared. 0 This same check scheme is efiective for other combinations as will be pointed out in detail later. p r I Other features of the present invention reside in the various circuit arrangements which are particularly adaptable for systems of this type.

In describing the invention in detail reference will be made to the accompanying drawing in which the various parts are designated by suitable reference characters. This drawing illus- 3O trates diagrammatically the apparatus and circuits provided in accordance with the present invention at a typical field station for the control of a single track switch and the signals for governing trafiic thereover. 35

For the purpose of simplifying the illustration and facilitating in the explanation, the various parts and circuits constituting the embodiment of the invention have been shown diagrammatically and certain conventional illustrations have 40 been employed. The drawing has been made more with the purpose of making it easier to understand the principles and mode of operation, rather than with the idea of illustrating the specific construction and arrangement of parts 45 that. would be employed in practice. For example, the various relays and the contacts are illustrated in a conventional manner with symbols employed to indicate the connections to the terminals of batteries or other source of direct 50 current instead of showing all the wiring connections to these terminals. The symbols and are employed to indicate the positive and negative terminals respectively of suitable batteries or other sources of direct current and the circuits with which these symbols are used always have current flowing in the same direction.

Communication system in generaZ.-A centralized traflic controlling system in which the present invention is more particularly useful consists of a control office and a number of outlying field stations. Communication is established between the control oifice and the field stations for the transmission of controls for governing the trafiic controlling devices at such stations and for the transmission of indications to give the operator in the control ofiice information as to the location of trains and the response of the various traific controlling devices. This communication is established over a station selective coded type communication system, in which a small number of line conductors is employed and in which the selective communication between the ofiice and any particular station, either for the transmission of controls and/or the transmission of indications, is established by the transmission of suitable codes.

For the purpose of illustrating the present invention it is considered unnecessary to illustrate the apparatus in the control o-fiice for applying a plurality of a series of different code combinations to the line circuit in accordance with the positions of code jumpers and control levers and it is also considered unnecessary to illustrate the reception of code combinations transmitted from the field stations to the control ofiice. It is assumed that a system for these purposes may be of any suitable character such for example as shown in the application of T. J. Judge, et al., Ser. No. 640,062, filed October 28, 1932, corresponding to British Patent 419,399.

It is considered sufiicient for an understanding of the present invention to merely illustrate how the control code part of each series of impulses results in the control of the traflic governing devices at a particular station and to indicate the relation of the apparatus shown with the rest of the apparatus of a complete system.

With reference to the accompanying drawing a control office has been merely indicated by a dotted rectangle. The control ofice is connected to the field station by three line wires, including a control line I9, an indication line l2 and a common return line hi, it being understood that these lines extend from the oflice to each of the field stations of the system. The line wires l0 and I2, together with the common return line wire M are so employed as to complete two line circuits namely, a control line circuit and an indication line circuit. The control line circuit is for the transmission of impulses of selected polarity from the control office to the field stations and includes at each field station a three position, polar, biased-to-neutral, line relay F.

The transmission of a series of distinctive impulses over the control line circuit results in the step-by-step operation of a stepping relay bank at each station, irrespective of the character of impulses, while the character of the impulses determine the particular field station to be selected. A station relay ST at each station is energized after the reception of the station selecting portion of the code combination which corresponds to the station at which this station relay is located. Relay ST corresponds to and may be considered as being operated in the same manner as station relay $0 of the above mentioned Judge et al. application.

At the particular station where the relay ST is selected, the remaining impulses of the cycle are effective to establish the proper control conditions. At those stations where the ST relays are not energized at the end of the station selecting portion of the cycle, the remaining impulses of the cycle are ineffective to establish control conditions.

For the transmission of indications to the control office, only one field station is rendered eiiective to transmit over the indication line circuit during any particular cycle. That particular station which is rendered effective, is selected by means of some suitable lockout arrangement. In any event, this selection of a field station for permitting it to transmit indications is made eifective at such station by the continued energization of its selecting or lockout relay throughout the cycle of operations, but since this particular portion of the system is immaterial for an understanding of the present invention the circuit arrangements relating to the transmission of indications are omitted.

Field station apparatus-The field station includes, besides the line relay F above mentioned, a neutral line repeating relay FP of the quick acting type, which is energized each time line relay F is energized, irrespective of the polarity of energization of relay F.

A slow acting neutral relay SA is picked up at the beginning of each cycle and is dropped at the end of each cycle, although it is energized only during the successive energizations of the control line circuit as repeated by relay FP. This is because relay SA has the proper slow acting characteristics.

In addition to the station relay ST above mentioned, a station stick relay STS is provided for checking the condition of the control apparatus at the start of a cycle, that is, if the control relays are all in their normal, de-energized positions at the start of the cycle relay STS will be picked up to connect these control relays to the control buses for receiving the coded impulses. If one or more of the control relays is picked up at the start of a particular cycle then relay STS cannot be picked up, with the result that no control code except the stop code can be received during this cycle.

The field station includes a stepping relay bank which takes one step for each de-energized condition of the control line. Although the stepping relays have been indicated as being picked up during the de-energized periods of the control circuit, so that the energized condition of the control line circuit may be directly executed or stored .on each step, it is understood that these operations can be reversed if desired.

.A slow acting last step relay LV is indicated as being operated in conjunction with the other stepping relays of the bank, this relay being picked up on the last step of the cycle. Due to its slow acting characteristics it is not dropped at the end of the cycle until a period of time has been measured off after the other stepping relays have been de-energized.

Although the field station is illustrated as including but a single track switch TS it will be understood that any number of track switches may be similarly controlled at a field station. Track switch TS is operated from one extreme locked position to the other by a suitable switch machine SM which may be of any suitable type known to those skilled in the art.

Associated with the track switch and the switch machine, a switch box or point detector contacts (not shown) are provided for controlling a switch position repeating relay. This switch repeating relay is not shown but it may be of the polar neutral type for repeating the position and the locked or unlocked condition of the track switch in a manner familiar to those skilled in the art.

Suitable signals lA-iB and 2A-2B are provided for governing trafiic over the track switch according to the usual practice. Although these signals have been illustrated as of the color light type, they may be of any other suitable type governed in accordance with the present invention. These signals are normally at stop but are cleared whenever their corresponding signal control relays (not shown) are energized, subject to the usual automatic block protection. Such control has been indicated in the drawing by conductors RW, NW, RE. and NE leading to the bracket which indicates that these conductors are connected to signal control relays for clearing signals 2B, 2A, H3 and IA respectively. It will be understood that these signal clearing circuits are governed in accordance with the position of the switch repeating relay and also in accordance with trafiic conditions in advance, all of which need not be shown for a proper understanding of the present invention.

The track switch TS also has associated therewith the usual detector track section, having the usual track battery and track relay T. A slow acting relay TP is provided for directly repeating the track relay Tfor purposes that will be later pointed out.

For the purpose of controlling the operation of switch machine SM, two switch machine control relays WN and WR of the neutral type have been provided. With relay WN energized and relay WR de-energized the circuits are so arranged that the switch machine will be operated to its normal locked position. With relay WR energized and relay WN de-energized the switch machine will be operated to its reverse locked position. With these relays both energizedor both de-energized the circuits are so arranged that the switch machine circuits are not energized for operating the switch machine in any manner.

The direction of trafiic over the track switch is determined by the direction control relays LD and RD, only one of which may remain up at any one time for controlling the signals. The particular route for the direction selected by these relays is determined by the position of the switch control relays WN and WR and as above mentioned in correspondence with the switch repeating relay (not shown).

Various other apparatus and devices for the field station includes a change relay, indication determining contacts and the like, all of which have been omitted for the purpose ofsimplifying the present disclosure.

It is believed that further characteristic functions and features of the invention will be best understood by considering various typical operations of the present embodiment.

Operation As above mentioned the first part of each different series of impulses forms a combination To that may be termed a station code call for the selection of a particular station, while the later part of each difierent series forms a combination for controlling the various devices at the selected station. Consideration of the station code calls will be given only general mention,

while detailed consideration will be given the later or control code part of each diiTerent series of impulses.

With the possibility of having either a positive or a negative impulse for each step the number of possible code combinations is equal to two raised to the power of the number of steps. In the present illustration the first two steps have been employed for the station selection part of the code. (3, 4, and 5) have been employed for the control codes and with the impulses for these three steps arranged in code combinations, eight different codes may be formed as illustrated in the table given below.

Table of control codes First Second Third Code no. step Step Step Code use Switch normaLsignals stop. Switch normal, signals east. Switch normal, signals I west. Not used. Switch reverse, signals stop. Switch reverse, signals cast. Switch reverse, signals we Not used.

More specifically there is a group of control levers in the control oiiice for each field station. The positioning of the levers for a particular station, followed by the actuation of suitable means to initiate the system, causes the transmission of a series of impulses comprising the code call for that station and the control code for operating the switch and controlling the signals at the selected station.

Following the transmission of the station code call, the control code is impressed upon the control line circuit as determined in accordance with the positions of the control levers for the particuiar station. In the examples chosen it is assumed that there is a signal control lever and a switch control lever, thus requiring three successive impulses to make the required combinations, as illustrated in the above table. It will be understood that the headings in this table, first step, second step, and third step refer to the first, second and third steps (3V, 4V and 5V) after station selection. 7

It is assumed that these codes are transmitted when the control levers are in their proper positions to give the desired controlling conditions at the field station as assigned to each code combination in the table. For example, if the switch lever is in a normal position and the signal lever is in an east clearing position, the second code will be transmitted consisting of This code is efiective to position the track switch TS in a normalposition and to clear east bound signal IA.

Station selection and step-by-step operati0at. At the beginning of a cycle of operations relay 1''? is energized by polar contact ll of relay F in either a right or a left hand position, depending upon the polarity with which line relay F is energized. .The closure of front contact I3 of relay FP energizes slow acting relay SA, which picks up after a short interval of time, remains picked up throughout the cycle and drops after the expiration of an interval of time after the control line has been de-energized at the end of the cycle.

The next three steps Upon the first de-energization of the control line, as repeated by relay FP following its first energization (relay SA being picked up) the first stepping relay is picked up and similarly. during each following de-energized condition of the control line circuit a succeeding stepping relay is picked up, so that after the station has been selected by the energization of relay ST, the control steps are then taken by stepping relays 3V, 4V and 5V. After the station is selected by the picking up of relay ST, the succeeding impulses in the control line circuit are effective to energize the control buses by way of contact I l of relay F, as determined by the polarity of the impulses received from the line circuit. .These buses have been given reference characters 6+, 2+, 2 3+, 3 to indicate that they are energized with the polarity indicated at the step indicated by the preceding numeral.

Normal conditions.As previously mentioned the detector track section associated with the track switch is of the normally closed track circuit type, so that the track relay T is normally energized as is readily understood. With the front contact 3! of relay T closed, an obvious energizing circuit for its repeating relay TP is closed. It will also be understood that the red or stop indicators of the signals IA!B and 2A2B are energized under normal conditions, since all signals normally indicate stop.

It will be assumed that the last previous operation of the system was the reception of a stop code, so that all of the other relays shown on the drawing are in their normal conditions.

Reception of control impulses-Jr the character of the first impulse is positive, then the normal switch machine control relay WN is energized, while if the character of the first impulse is negative the reverse switch machine control relay WR is energized. At the first step of the cycle circuits are closed for energizing both signalrelays RD and LD, then if the character of the second impulse is positive relay LD will be (is-energized and relay RD will remain energized. If the character of the second impulse is negative relay RD will be de-energized and relay LD will'rernain energized. If the character of the third impulse is positive relay RD will be de-energized and if the character of the third impulse is negative relay LD will be de-energized.

More specifically, as soon as thestation is selected relay ST is energized and closes a circuit for picking up relay STS extending from front contact 29 of relay ST, back contact 2| of relay WR, back contact 22 of relay WN and winding of relay STS to Relay STS closes a stick circuit for itself extending from front contact 20 of relay ST, front contact 23 and winding of relay STS to .Relay ST, at its front contact it, connects to contact ll of relay F, so that the following impulses will be effective to energize the code conductors in the various combinations presently to be explained.

With relay STS picked up a circuit is closed for picking up relay RD (when the third step is taken) which extends from back contact 24 of relay lV, front contact 25 of relay 3V, front contact 26 of relay STS and upper winding of relay RD to A circuit is closed for picking up relay LD which extends from back contact 2? of relay 4V, front contact 28 of relay 3V, front contact 29 of relay STS and upper winding of relay LD to Relays RD and LD close stick circuits for themselves including their front contacts 35 and 36 to at front contact 31 0f relay T. It will be noted that the picking up of both relays RD and LD is ineffective to close any signal clearing circuits because back contact 38 of relay LD is open and back contact 39 of relay RD is open.

Code No. 1.The impulse received on the first step positions relay F to the right for closing a circuit for picking up relay WN extending from front contact I6 of relay ST, contact I? of relay F in its right hand dotted position, back contacts l8 and IQ of relays 5V and 4V respectively, front contact 30 of relay 3V, l+ bus, front contact 40 of relay STS and winding of relay WN to Relay WN closes a stick circuit for itself extending from front contact H of relay STS, front contact 42 and winding of relay WN' to It will be understood that relay STS is de-energized at the end of the cycle when relay ST opens its front contact 20 to de-energize the stick circuit of relay STS.

The impulse received on the second step closes a circuit for de-energizing relay LD which extends from front contact l6 of relay ST, contact I! of relay F in its right hand dotted position, back contact I8 of relay 5V, front contact IQ of relay 4V, 2+ bus, front contact 46 of relay STS, front contact 41 and lower winding of relay LD to Since relay LD has its upper winding energized in the direction indicated by the arrow associated with this winding and since the last traced circuit energizes its lower winding in the direction of the arrow associated with this winding, the relay will be deenergized because of the neutralizing effects of these two windings on the armature.

The reception of impulse 3+ closes a circuit for de energizing relay RD in a manner similar to that explained in connection with relay LD, which circuit extends from front contact E6 of relay ST, contact I! of relay F in its right hand dotted position, front contact I8 of relay 5V, 3+ bus, front contact 48 of relay STS, front contact 49 and lower winding of relay RD to With relays RD and LD de-energized there is no circuit closed for clearing any of the signals, because front contacts 38 and 58 of relays LD and RD respectively are open. Since relay ST drops before relay STS, the stick circuit of relay WN is maintained energized at back contact 20 of relay ST so that relay WN remains picked up.

The switch machine is now operated to its normal position over a circuit extending from front contact 53 of relay WN, back contact 44 of relay STS, normal operating wire N, switch machine motor, reverse operating wire R and back contact ili'of relay WR to The above described code is one that is conveniently used when all signals are at stop, for operating the switchmachine to normal without clearing a signal. This is of advantage in clearing the switch of obstructions due to ice and the like.

Code N0. 2.The number impulse of this code is eifective to pick up relay WN and this relay is stuck up in the manner previously described. The number 2+ impulse is effective to kick down relay LD as above pointed out. The number 3- impulse is ineffective, since the circult of this code bus extends through front contact 59 of relay STS to the same contact (41) on relay LD as used by the 2+ impulse for deenergizing this relay. Therefore impulse 3- is ineffective with the result that the end of the cycle is reached with. relays WN and RD energized. The dropping of relay STS closes its back contact 44. for operating the switch machine iii to its normal position by way of front contact 43 of relay WN. A circuit is now closed for clearing signal IA which extends from back contact 38 of relay LD, front contact 58 of relay RD, back contact 59 of relay WR, front contact 57 of relay WN and normal east conductor NE to signal EA.

Code No. 3.-The 9+ impulse is efiective as before to operate the switch machine to its normal position when relay STS drops at the end of the cycle with relay W'N picked up. The 2 impulse closes a circuit for de-energizing relay RD which extends from front contact 16 of relay ST, contact ll of relay F in its left hand dotted position, back contact 32 of relay 5V, front contact 33 of relay 4V, 2 bus, front contact 56 of relay STS, front contact 49 and lower winding of relay RD to Relay RD is kicked down by this circuit. The 3+ impulse is ineffective since front contact 49 of relay RD is now open. Signal 2A is cleared over a circuit extending from front contact 38 of relay LD, back contact 39 of relay RD, back contact 52 of relay WR, front contact 53 of relay WN and normal west conductor NW to signal 2A.

Code No. 4.This code is not used but it will be later explained what happens in the event that this code is inadvertently received, due to the reception of a wrong impulse in connection with one of the other code combinations.

7 Code No. 5.The number I-- impulse closes a circuit for picking up relay WR extending from front contact [5 of relay ST, contact I! of relay F in its left hand dotted position, back contacts 32 and 33 of relays 5V and 4V respectively, front contact 34 of relay 3V, lbus, front contact 54 of relay STS and winding of relay WR to Relay WR closes a stick circuit for itself extending from front contact ll of relay STS, front contact 55 and winding of relay WR to This stick circuit is maintained energized after the completion of this cycle of operations at back contact 20 of relay ST. At the end of the cycle a circuit is closed for operating the switch machine to its reverse position extending from front contact of relay WR, reverse conductor R, switch machine motor, normal conductor N, back contact 46 of relay STS and back contact 43 of relay WN to Since this is a stop code used when it is desired to operate the switch machine to its reverse position without clearing any of the signals, the 2+ and 3+ impulses are effective to kick down relays LD and RD as before.

Code No. 6.-The number I impulse is effective to operate the switch machine to its reverse position as just described. The 2+ and 3 impulses are effective to kick down relay LD and to leave relay RD energized as described in connection with Code Number 2. With relay WR up, relay WN down, relay RD up and relay LD down, a circuit is closed for clearing signal IB which extends from back contact 38 of relay LD, front contact 58 of relay RD, front contact 59 of relay WR, back contact of relay WN and reverse east conductor RE to signal lB.

Code No. 7.The number 1- impulse is effective as before for operating the switch machine to reverse. The No. 2- and 3+ impulses are effective as in Code No. 3 to kick down relay RD and leave relay LD energized. A circuit is closed. for clearing signal 2B which extends from front contact 38 of relay LD, back contact 39 of relay RD, front contact 52 of relay WR, back contact 60 of relay WN and reverse west conductor RW to signal 2B.

Code No. 8.This code combination is not used in the present embodiment, but the combination of impulses in this code which may be received 1 due to the reception of a wrong code is effective to produce certain results which will be later described.

When any of the signals are cleared, the occupancy of the track section results in relay T being de-energized to drop its front contact 37. This de-energizes the stick circuits of the RD and LD relays, so'that the energized one of these relays will be de-energized to put all signals to stop, by opening front contacts 38 and 58 of these relays. Shortly after relay T drops its contacts, relay TP is de-energized to close its back contact 6| which again energizes the stick conductor of the direction relays. Therefore a code may be transmitted, received and stored while the track section is occupied. It will be understood that this code is not effective to clear a signal while the train is in the track section, because of certain correspondence and lock circuits which are provided andwhich are familiar to those skilled in the art. Therefore these additional circuits need not be explained in connection with the presentdisclosure.

For convenience in describing how a route may be put to stop, it will be assumed that the track switch TS is in a reverse position and. the signal 213 has been cleared as previously described. This route may be put to stop by the passage of a train over the detector track section as previously described, or by manual manipulation of the control lever in the control office. It will now be explained how this stop code (either or is received and how it puts the cleared route to stop.

Since a stop control code need be received only when a route is actually cleared, the reception of the stop code can be made dependent upon the prior reception of 2. proceed code. Since it is assumed that the switch is in-a reverse position with signal 23 cleared the previous proceed code was resulting in control relays WR and LD being up.

Since relay WR is up and its back contact 2| open,'relay STS cannot be picked up at the start of this cycle. orv is not effective to energize either of the switch control relays, because the 1+ and the 1 buses are open at front contacts 40 and 54 respectively of relay STS. The number 2+ impulse is efiective to pick up stop relay IS over a.

circuit extending from front contact I6 of relay ST, contact I! of relay F in its right hand dotted position, back contact l8 of relay 5V, front contact 19 of relay 4V, 2+ bus, back coritact 46 of relay STS, back contact 62 of relay 2S and upper winding of relay IS to Relay IS closes a stick circuit for itself extending from front contact 63 of relay ST, front contact 64 and upper winding of relay IS to The 3+ impulse closes a circuit for picking up relay 28 extending from front contact I6 of relay ST, contact ll of relay F in its right hand dotted position, front contact 18 of relay 5V, 3+ bus, back contact 48 of relay STS and winding of relay 2S to Relay 2S closes an obvious stick circuit for itself at its front contact 65.

At the end of the cycle, relay SA closes its back contact 66 before relay LV opens its front contact iil, so that a momentary impulse is extended through these two contacts and through front Therefore, the first impulse either contact 68 of relay 2S, front contact 69 of relay IS, front contact 10 and lower winding of relay LD to This momentary impulse kicks down relay LD and since relayRD is already down all signals are put to stop. With both front contacts 1| and 72 of relays RD and LD, respectively, down and with front contact 4| of relay STS down, the stick circuit for relays WN and WR B de-energized before relay ST drops its contact 20 at the end of the cycle. This results in de-energizing relay WR so that all of the control relays WN, WR, RD, and LD are restored to normal. Relays IS and 2S arede-energized when relay ST drops its front contact 63 at the end of the cycle.

It will be evident that the stop code is effective to pick up the IS and 2S relays during a cycle, at the beginning of which relay STS could not be picked up because some signal was cleared. It is believed that the above example is sufficient to indicate that this stop code is effective with either of the switch control relays or either of the direction relays picked up. In the event that relay RD is picked up to clear an east bound signal, then the reception of a stop code is effective to kick down relay RD by means of the previously described circuit now extending through front contacts I68 and IE9 of the stop relays, front contact I3 and lower winding of relay RD to With reference to the above code table it is apparent that the track switch can be operated to normal or reverse positions at the will of the operator, without clearing a route by the use of Codes 1 and 5 respectively. The use of such codes to eifect the operation of the track switch must be transmitted after the signals have been put to stop, because the switch control relays can not be changed in their positions while a signal is clear. This is due to the fact that either direction relay maintains the stick circuit for the switch control relays energized and this condition prevents the picking up of relay STS at the beginning of a cycle, so that it is necessary to transmit a stop code for restoring these control relays to normal before the track switch can be operated without clearing a signal.

Reception of wrong codes-An important feature of the present invention relates to the arrangement of the codes and the circuits controlled by these codes for preventing the faulty operation of the track switch, the clearing of a wrong signal or the putting of signals to stop upon the reception of an improper code. The following explanation will be devoted to the code combinations which are used for operating the switch machine and clearing the signals in various combinations, as given in the above code table.

Code No. 1.It will first be assumed that some signal is clear when this code is received. Since relay STS cannot be picked up the only code buses effective are 2+, 2-, 3+ and 3-. Therefore a 1+ or a 1- impulse is ineffective to change anything. If the second impulse is and received in this order, the 2+ impulse will pick up relay I S and the 2- impulse will immediately kick it down. The circuit for kicking down relay IS extends from front contact I6 of relay ST, contact I I of relay F in its left hand dotted position, back contact 32 of relay 5V, front contact 33 of relay 4V, 2- bus, back contact 5I of relay STS, front contact I4 and lower winding of relay IS to If the 2 impulse is received first, relay 2S will be picked up over a circuit extending through back contact I4 of relay IS. Then the 2+ impulse is ineffective becauseback contact 62 of relay 28 is open. If the third impulse is 3+ relay 2S will be picked up, if not already up, but in any event relay IS is down. If the third impulse is 3- this impulse is inefifective because relay IS is down and its front contact I5 is open. With front contacts 68 and I69 of relay IS open the stop code is ineffective to put signals to stop.

If 2+ only is received on the second step relay IS will be picked up then if a 3- is received on the third step, either alone or with a 3+, relay IS will be kicked down. Since both stop relays must be up to render the stop code effective it will be seen that a reception of a wrong code, an extra impulse or the omission of an impulse will prevent the cleared signals being put to stop by preventing both stop relays being up when relay SA drops its contact 65 at the end of the cycle.

It will now be assumed that all signals are at stop at the beginning of a cycle during which Code No. l is received. This means that relay STS will be picked up at the start of the cycle. If a and a impulse are received on the first step, both the 1+ and the 1- buses will be energized to pick up relays WN and WR. With both contacts 43 and 45 of these relays picked up the switch machine motor cannot be energized and since contact 34 of relay STS is picked up at the time that the number. 1 impulse is received it makes no diiference which relay WN or WR is picked up first.

With both relays WN and WR picked up no signal can be cleared, because the signal clearing circuits require that one or the other of these relays be down. If the second impulse received is both and both the 2+ and 2- buses are energized which results in kicking down relays LD and RD so that no signal will be cleared. Upon the reception of a and a impulse at the third step, both buses 3+ and 3 will be energized for kicking down relays RD and LD so that no signal can be cleared. It will thus be seen that under this condition the reception of an extra impulse in connection with a stop code is ineffective to falsely clear a signal.

Code No. 2.The reception of a surge at the first step which energizes buses 1+ and 1- will pick up relays WN and WR so that no signal can be cleared and the switch machine position cannot be changed, for the reasons described in connection with Code No. 1. The reception of and impulses at the second step kicks down both direction relays so that no signal can be cleared. The reception of and impulses at the third step kicks down both direction relays so that no signal can be cleared.

Code No. 3.The reception of two impulses at the first step in connection with this code effects the same operation as described in connection with Code No. 1. The reception of and impulses at the second step kicks down both direction relays, because the energization of buses 2+ and 2- energize the lower windings of these two relays in opposition to their upper windings as previously described. Similarly the reception of and impulses at the third step kick down these direction relays in the previously described manner.

It is believed unnecessary to describe the detailed operation of the result due to the reception of surges in connection with the other three codes, since the surges affect the control relays in the same manner already described. In the event that an impulse is not received for a sufficient time to energize the'control buses for picking up the switch control relays, or for kicking down the direction relays the result is that no wrong condition will be efiected. This is because with both relays WN and WR. down the switch machine can-. not be operated and a signal cannot be cleared and with both relays RD and LD up no signal can be cleared.

In connection with the signal clearing codes, the reception of a wrong code at any one step is ineffective to clear a signal but the control cir cuits will be left in the conditions last assumed. For example, in connection with Code No. 2, if the second impulse is received instead of in Code No. 2 and the third impulse is properly received energizing the 2- bus on the second step kicks down relay RD and em ergizing the 3- bus on the third step kicks down relay LD so that no signal will be cleared.

If the second impulse is properly received relay LD will be kicked down, then if the third impulse is improperly received relay RD will be kicked down and no signal will be cleared.

It is believed that the above examples are sufiicient to indicate how the present invention is arranged for checking against extra impulses received, due to surges or the like, vagainstwro'ng impulses received and against the absence of impulses at the difierent steps of the cycle.

The system contemplated by the present invention is arranged so that correspondence is re-' quired between the track switch and the switch control relays, so that a route cannot be cleared without the proper response of the switch machine. Since this portion of the system is immaterial'to an understanding of the features of the present invention it has been omitted from the present disclosure for the sake of simplicity. Such correspondence circuits may be as disclosed in the prior application of T. J. Judge, Ser. No. 678,045, filed June 28, 1933.

These various features and others which are apparent from a study of the above description, provides a safe and reliable control for the traffic controlling devices through the medium of a code type communication system.

Having thus described a centralized traffic controlling system as one embodiment of the present invention, it is desired to be understood that this form is selected to facilitate in the disclosure of the invention rather than to limit the number of forms which it may assume and it is to be further understood that various modifications, adaptations and alterations may be applied to the specific form shown to meet the requirements of practice, without in any manner departing from the spirit or scope of the present invention, except as limited by the appended claims.

What I claim is:

1. In combination, a track switch. signals for governing trafiic over said track switch, clearing circuits for said signals; a line circuit having a series of coded impulses successively transmitted thereover, means for storing an initial code of said series .and concomitantly therewith effecting selection of one of said clearing circuits, means responsive to a second code of said series for energizing said selected clearing, circuit, and means responsive to a third code of said series for confirming said selection.

2. In combination, a track switch, signals for governing traific over said track switch, clearing circuits for said signals, a line circuit having a series ofv coded impulses successively transmitted thereover, means for storing an initial code of said series and concomitantly therewith efiecting selection of one of said clearing circuits, and

means responsive to a subsequent code of said series for cancelling said selection.

3. In combination, a track switch, signals for governing traflic over said track switch, clearing circuits for said signals, a line circuit having a series of characteristic impulses successively transmitted thereover, means for receiving said impulses, means responsive to the reception or an impulse of said series for preparing one of said clearing circuits, means responsive to the reception of succeeding impulses of said series of unlike character for completing said prepared circult, and means responsive to the reception of succeeding impulses of said series of like charac. ter for annulling said prepared circuit.

4. In combination, a track switch, signals for governing trafiic over said track switch, a clearing circuit for each of said signals, a line circuit having a series of impulses transmitted thereover, means for registering said impulses, means re-" sponsive to a first one of said impulses for controlling said track switch and for selecting a plurality of said clearing circuits, means responsive to a second one of said impulses for selecting and energizing one of said plurality of clearing circuits, and means responsive to a third one of said impulses for immediately deenergizing said energized clearing circuit.

5. In combination, a track switch, signals for governing trafiic over said track switch, a clearing circuit for each of said signals, a line circuit having a series of impulses of predetermined character transmitted thereover, means for selectively registering the character of said impulses, means responsive to a first one of said impulses for controlling said track switch and for selecting a plurality of said clearing circuits, means responsive to a second one of said impulses for selecting and energizing one of said plurality of clearing circuits, and means responsive to a third one of said impulses for immediately deenergizing said energized clearing circuit.

6. In combination, a track switch, signals for governing trafiic over said track switch, a clearing circuit for each of said signals, a line circuit having a series of impulses of predetermined character transmitted thereover, means for selectively registering the character of said impulses, means responsive to a first One of said impulses for controlling said track switch and for selecting a plurality of said clearing circuits, means responsive to a second one of said impulses for selecting and energizing one of said plurality ofclearing circuits, means responsive to a third one of said impulses of one character for immediately deenergizing said energized clearing circuit, and means responsive to a third one of said impulses of another character for preventing the deenergization of said energized clearing circuit.

'7. In combination, a line circuit having a series of positive and negative impulses forming a code transmitted thereover, a polar relay included in said line circuit, step-by-step mechanism operable to take one step for each of said impulses, a pair of control relays, energizing circuits for said pair of control relays closed at one step of said mechanism, and deenergizing circuits for said'pair of control relays selected by said polar relay and closed on another step of said mechanism. I

8. In combination. a line circuit having a series of positive and negative impulses forming a code transmitted thereover, a polar relay included in said line circuit, step-by-step mechanism operable to take one step for each of saidimpulses, a pair of control relays, energizing circuits for said pair of control relays closed at one step of said mechanism, and differential deenergizing circuits for said pair of control relays selected by said polar relay and closed on another step of said mechanism.

9. In combination, a line circuit having a series of impulses of distinctive character transmitted thereover, step-by-step mechanism operable to take one step for each of said impulses, a pair of control relays selectable at a particular step of said mechanism and energized at a previous step of said mechanism, means responsive to the character of an impulse of one character received at said particular step for selectively deenergizing one of said control relays, and means responsive to the reception of an impulse of another character at said particular step for deenergizing the other of said relays.

10. In a centralized trafiic controlling system, a track switch, a switch machine for operating said track switch, signals for governing traffic over said track switch, a line circuit having series of characteristic impulses transmitted thereover to form distinctive signal clearing and stop code combinations, means for receiving said impulses, step-by-step mechanism operable through a cycle one step for each impulse of a series, switch machine control means responsive to a switch code received during a cycle, signal clearing means responsive to a signal code received during a cycle, stop control means responsive to a stop code received during a cycle, a selecting relay, means controlled by said selecting relay for rendering said switch control and said signal clearing means operable by said mechanism only when said switch control and said signal clearing means are inactive at the start of a cycle, and means for rendering said switch control and said signal clearing means inactive in response to a stop code when and only when some part of said switch control means or said signal, clearing means is active at the start of a cycle.

11. In a centralized trailic controlling system, a track switch, a switch machine for operating said track switch, signals for governing traffic over said track switch, a line circuit having series of characteristic impulses transmitted thereover to form distinctive signal clearing and stop code combinations, means for receiving said impulses, step-by-step mechanism operable through a cycle one step for each impulse of a series, switch machine control means responsive to a switch code received during a cycle, signal clearing means responsive to a signal code received during a cycle, stop control means responsive to a stop code received during a cycle, a selecting relay, means controlled by said selecting relay for rendering said switch control and said signal clearing means operable by said mechanism only when said switch control and said signal clearing means are inactive at the start of a cycle, means for rendering said switch control and said signal clearing means inactive in response to a stop code when and only when some part of said switch control means or said clearing means is active at the start of a cycle, and means controlled by said relay for preventing the operation of said switch machine during a cycle at the start of which said switch control and said signal clearing means are inactive.

12. In combination, a switch machine for operating a railroad track switch, a line circuit having a plurality of positive and negative imwith said code combination only when said station repeating relay is rendered active, and means for allowing said switch machine to be controlled by said code receiving relays only when said station repeating relay is rendered inactive.

13. In combination, a railroad track section, a track switch associated with said section, signals for governing traffic over said track switch, clearing circuits for said signals, a line circuit having a series of characteristic impulses successively transmitted thereover, means for receiving said impulses, means responsive to the reception of an impulse of said series for preparing one of said clearing circuits, means responsive to the reception of succeeding impulses of said series of unlike character for completing said prepared circuit, means responsive to the reception of succeeding impulses of said series of like character for annulling said prepared circuit, and means controlled by the occupancy of said section for annulling said prepared circuit.

14. In combination, a line circuit having a series of positive and negative impulses forming a code transmitted thereover, a polar relay included in said line circuit, step-by-step mechanism operable to take one step for each of said impulses, a pair of control relays, energizing circuits for said pair of control relays closed at one step of said mechanism, stick circuits for said pair of control relays, deenergizing circuits for said pair of control relays independent of said stick circuits selected by said polar relay and closed on another step of said mechanism, and means for deenergizing said pair of control relays by the deenergization of said stick circuits.

15. In combination, a, line circuit having a series of impulses of distinctive character transmitted thereover, step-by-step mechanism operable to take one step for each of said impulses, a pair of control relays selectable at a particular step of said mechanism and energized at a previous step of said mechanism, a track section including a track switch governed by said control relays, means responsive to the character of an impulse of one character received at said particular step for selectively deenergizing one of said control relays, means responsive to the reception of an impulse of another character at said particular step for deenergizing the other of said relays, and means controlled by the occupancy of said section for deenergizing both of said relays.

16. In combination, two control relays each having active and inactive positions, conditioning means for simultaneously operating said control relays, a normally energized stick circuit for said control relays, a first control means for selectively and individually releasing said control relays, a second control means independent of said stick circuit for simultaneously releasing said control relays, a third control means for releasing said control relays by deenergizing said stick circuit, and a plurality of channel circuits selectively energized in accordance with the positions of said control relays.

17. In combination, a line circuit over which combinations of impulses comprising signal clearing and stop codes are transmitted, a code receiver connected to said line circuit for receiving said codes, a railroad track switch and a plurality of signals associated with said code receiver, a plurality of signal control relays for controlling said signals, means for energizing said control relays at the start of a code transmitted over said line circuit, means responsive to a signal clearing code for selectively de-energizing one of said relays whereby said signals are selectively cleared, and means responsive to a stop code for de-energizing said plurality of control relays whereby said signals are put to stop.

18. In combination, a line circuit over which combinations of impulses comprising signal clearing and stop codes are transmitted, a code receiver connected to said line circuit for receiving said codes, a railroad track switch and a plurality of signals associated with said code receiver, a plurality of signal control relays for controlling said signals, means for energizing said control relays at the start of a code transmitted over said line circuit, means responsive to a signal clearing code for selectively de-energizing one of said relays whereby said signals are selectively cleared, a stop relay, means responsive to a stop code for energizing said stop relay, and means effective at the termination of said stop code and including said stop relay for de-energizing said control relays whereby said signals are put to stop.

19. In combination, a line circuit over which combinations of impulses comprising signal clearing and stop codes are transmitted, a code receiver connected to said line circuit for receiving said codes, a railroad track switch and a plurality of signals associated with said code receiver, a plurality of signal control relays for controlling said signals, means for energizing said control relays at the start of a code transmitted over said line circuit, means responsive to a signal clearing code for selectively de-energizing one of said relays whereby said signals are selectively cleared, a stop relay, means responsive to a stop code for energizing said stop relay, means effective at the termination of said stop code and including said stop relay for de-energizing said control relays whereby said signals are put to stop, and means responsive to the occupancy of the track section with which said track switch is associated for deenergizing said control relays whereby said signals are put to stop.

20. In combination; a line circuit over which combinations of impulses comprising receiver selecting, signal clearing and stop codes are transmitted; a code receiver; means responsive to a receiver selecting code for selectively associating said code receiver with said line circuit; means including said code receiver for receiving said signal clearing and stop codes; a railroad track switch and a plurality of signals associated with said code receiver; a plurality of signal control relays for controlling said signals; means for energizing said control relays at one point of a code transmitted over said line circuit; means responsive to a signal clearing code for selectively de-energizing one of said relays whereby said signals are selectively cleared; and means responsive to a stop code for de-energizing said plurality of control relays whereby said signals are put to stop.

21. In a selecting system; a transmitting station and a receiving station connected by a line circuit, said line circuit being energized with impulses of variable polarity; a plurality of differential relays at said receiving station each having two similar windings; means at said receiving station controlled over said line circuit for picking up said relays by simultaneously energizing a first winding of each relay in response to one of said impulses; and means controlled by the polarity of other impulses received over said line circuit for releasing said relays by energizing their second windings.

22. In a selecting system; a transmitting station and a receiving station connected by a line circuit, said line circuit being energized with impulses of variable polarity; a plurality of difierential relays at said receiving station each having two similar windings; means at said receiving station controlled over said line circuit for picking up said relays by simultaneously energizing a first winding of each relay in response to one of said impulses; means for sticking said relays by energizing stick circuits connected to said first windings; and means controlled by the polarity of other impulses received over said line circuit for releasing said relays by energizing their second windings.

23. In a selecting system; a transmitting station and a receiving station connected by a line circuit, said line circuit being energized with impulses of variable polarity; a plurality of differential relays at said receiving station each having two similar windings; means at said receiving station controlled over said line circuit for picking up said relays by simultaneously energizing a first winding of each relay in response to one of said impulses; means for sticking said relays by energizing stick circuits connected to said first windings; and means controlled by the polarity of another of said impulses received over said line circuit for selectively releasing one of said relays by energizing its second winding.

WINFRED T. POWELL. 

